1. Technical Field
This invention relates generally to methods for managing telephone calls to multiple extensions. More particularly, the invention relates to a method for managing telephone calls to a plurality of extension communication units through the use of directories to reach the correct extension.
2. History of Related Art
Currently, methods for providing extension management services within a mobile radio telephone communication system include systems that determine which telephone receives a call based on a predefined priority protocol assigned to each extension communication unit, which is typically a cellular telephone or some other type of mobile station. The priority is based upon the first subscriber to answer the call, the extension communication unit closest to the calling party, or the extension communication unit with the highest assigned priority (see, generally, FIG. 1).
In such prior art systems, a call directed to a single subscriber number is received at a gateway MSC, which in turn sends a location request message to an associated HLR. In response to the location request message, the HLR transmits an individual routing request message to each one of the plurality of identified MSC""s serving extension communication units associated with the subscriber number. In turn, each one of the MSC""s receiving a routing request message pages each one of the assigned extension communication units within its service area. A voice channel is established between any responding extension communication units and its corresponding paging MSC. Each responding extension communication unit is alerted, preferably with a distinctive ring, so that the associated subscriber knows that this is an extension communication unit call.
If a subscriber is present and answers the call, then the answering subscriber is put on hold while the corresponding MSC returns the result to the associated HLR. If more than one MSC returns a result to the HLR (indicating that more than one subscriber answered the call), then the HLR selects a single subscriber to complete the call, based on one of the three possible predetermined criteria described above. Following delivery of the call, the HLR releases all of the answering extension communication units that were not selected by the HLR to receive the call.
Several problems exist with this type of system. The call might be routed to the wrong extension communication unit due to the use of a non-current, predefined priority table, so that the person making the call has to call again or leave a message. Also, when the call is completed by one of the extension communication units, other extensions associated with the subscriber number will not receive a chance to participate in the call because its transmission to them is cancelled by the system. Thus, this system does not allow all of the subscribers having extension communication units associated with the same subscriber number to have the same priority for answering a call.
What is needed, therefore, is a method of managing a plurality of extension communication units which ensures that a call reaches the proper mobile extension. More particularly, what is needed is a method which primarily utilizes a current directory to identify those extension communication units which will receive the call and secondarily utilizes a conference call decision-making process allowing the subscribers, rather than the system, to determine who will take the call. The method should permit all of the subscribers to have the same priority for answering a call. Finally, the method should utilize the minimum amount of system resources necessary in order to route the call to the correct extension communication unit without the necessity of additional calls and/or messages being made.
The present invention includes a method for managing a plurality of mobile extension communication units using a directory and a conference call decision-making process. In this method, a location request message associated with a call to a subscriber number is received. A determination is made as to whether more than one mobile identification number (MIN) is associated with the subscriber number to which the call is directed. If not, the call is delivered to the mobile station corresponding to the MIN assigned to the subscriber number to which the call is directed. If so, a determination is made as to whether the Calling Party Number is included in the telephone directory corresponding to each of the MINs associated with the subscriber number. If the Calling Party Number is not included in a telephone directory corresponding to any of the MINs, the call is routed to all of the extension communication units. If the Calling Party Number is included in the telephone directory corresponding to only one of the MIN""s, then the call is delivered to the extension communication unit associated with that MIN. If the Calling Party Number is included in the telephone directories corresponding to two or more MIN""s, then the call is routed to those specific extension communication units. The Home Location Register (HLR) sends the routing request message for each MIN to the appropriate VLR/MSC, and the VLR/MSC pages each of the MIN""s. The HLR waits until all responses have been received. If there are no responses, the HLR initiates its recovery procedure and finishes the call. If there is at least one response, the call is delivered to the responding extension communication unit, while the HLR continues to collect all the routing numbers (TLDN""s) from each extension and send them to the GMSC in a location request return result response. A conference call countdown timer in the GMSC is initiated and all extensions not responding within the allotted time are released. Each extension answering within the allotted time is included in a conference call (assuming more than one extension answers). If another extension has already answered the call and activated a selected function code, other extensions which have answered, or subsequently answering the call, will be canceled and released. Thus, multiple extensions may respond at different points within the allotted conference call answering response time to join a conference call. Once the time limit has passed, it is no longer possible for the non-answering extensions to join the conference call. An additional feature includes a change in the ring tone after one extension has answered the call in order to alert remaining extensions that the call has been answered by at least one extension.
In another embodiment of the invention, a node in electronic communication with the plurality of extension communication units includes a response reception module for receiving paging and answering responses from the extensions, and a conference call answering response timer in electronic communication with the response reception module. The node is in electronic communication with a HLR, which includes a paging response timer. Another embodiment of the invention includes an extension communication unit management system having a plurality of extension communication units in electronic communication with the node.